Tyrothricin
Encyclopedia
Tyrothricin is a cyclic polypeptide-antibiotic mixture from Bacillus brevis
Bacillus brevis
Aneurinibacillus migulanus , formerly known as Bacillus brevis is a Gram-positive aerobic spore-forming bacillus commonly found in soil, air, water, and decaying matter. It is rarely associated with infectious diseases...

. It is a locally effective antibiotic effective against gram-positive
Gram-positive
Gram-positive bacteria are those that are stained dark blue or violet by Gram staining. This is in contrast to Gram-negative bacteria, which cannot retain the crystal violet stain, instead taking up the counterstain and appearing red or pink...

 bacteria. It is sometimes combined with benzocaine
Benzocaine
Benzocaine is a local anesthetic commonly used as a topical pain reliever, or in cough drops. It is the active ingredient in many over-the-counter anesthetic ointments...

 5 mg to provide relief from sore throat
Sore throat
A sore throat or throat pain is a common physical symptom usually caused by acute pharyngitis, or throat inflammation, though it also occurs in a number of other situations, such as post trauma and in diphtheria. It can cause mild to extreme pain....

s. In systemic intake it can lead to severe side effects, therefore, the use is limited to topical application.

Tyrothricin belongs to the pharmacologically related group of polypeptide antibiotic compounds including colistin
Colistin
Colistin is a polymyxin antibiotic produced by certain strains of Bacillus polymyxa var. colistinus. Colistin is a mixture of cyclic polypeptides colistin A and B. Colistin is effective against most Gram-negative bacilli and is used as a lingerdoodle. It is one of the last-resort antibiotics for...

, polymyxin B
Polymyxin B
Polymyxin B is an antibiotic primarily used for resistant gram-negative infections. It is derived from the bacterium Bacillus polymyxa. Polymyxin B is a mixture of two closely related compounds, polymyxin B1 and polymyxin B2. It has a bactericidal action against almost all gram-negative bacilli...

 and bacitracin
Bacitracin
Bacitracin is a mixture of related cyclic polypeptides produced by organisms of the licheniformis group of Bacillus subtilis var Tracy, isolation of which was first reported in 1945....

. There are no cross-resistance to these three agents.

Effect

Tyrothricin inhibits protein biosynthesis
Protein biosynthesis
Protein biosynthesis is the process in which cells build or manufacture proteins. The term is sometimes used to refer only to protein translation but more often it refers to a multi-step process, beginning with amino acid synthesis and transcription of nuclear DNA into messenger RNA, which is then...

 of gram-positive
Gram-positive
Gram-positive bacteria are those that are stained dark blue or violet by Gram staining. This is in contrast to Gram-negative bacteria, which cannot retain the crystal violet stain, instead taking up the counterstain and appearing red or pink...

 organisms, but is completely ineffective against gram-negative
Gram-negative
Gram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color...

.

Application

The most common use for tyrothricin is inflammation of the throat
Throat
In vertebrate anatomy, the throat is the anterior part of the neck, in front of the vertebral column. It consists of the pharynx and larynx...

, gastric mucosa
Gastric mucosa
The gastric mucosa is the mucous membrane layer of the stomach which contains the glands and the gastric pits. In men it is about 1 mm thick and its surface is smooth, soft, and velvety...

, and angina tonsillaris. In order to use tyrothricin, the mucous membrane must be intact. This is to ensure that tyrothricin will not come into contact with the bloodstream, therefore limiting the risk of systemic absorption.

Side-effects

Known hypersensitivity reactions are common, temporary loss of balance (see Vestibular system
Vestibular system
The vestibular system, which contributes to balance in most mammals and to the sense of spatial orientation, is the sensory system that provides the leading contribution about movement and sense of balance. Together with the cochlea, a part of the auditory system, it constitutes the labyrinth of...

) and nephrotoxic effects, i.e. impairment of renal function. There are no long term studies about its effect on pregnancy and lactation.

Trade names

Separate preparations: Limexx (AT), Tyrosur (DE)

Compounds: Citropain (CH), Dorithricin (DE, AT), Lemocin (DE, AT, CH), Mebucaine (CH), Mebucasol (CH), Otothricinol (CH), Sangerol (CH), Solmucaine (CH), TYroqualin (CH) and generic (AT, CH), Tyrozets (UK)
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